An energy storage device which can store a massive amount of energy and which can rapidly charge and discharge is required for electric load-leveling (load-control) equipment as well as solar-power generation, wind-power generation or the like and for momentary-voltage drop-prevention systems using electronic hardware such as computers or the like and for energy-regeneration systems or the like used in electric vehicles and hybrid cars. Conventional types of lead batteries or other secondary batteries, which are not suitable for a high current charge-discharge and which have a short cycle life, have difficulties in being applied to such energy storage systems. As a new type of energy storage device to resolve such problems, a non-aqueous energy storage device draws now much attention.
As a rapid charge-discharge and longer-lasting non-aqueous energy storage device, a lithium-ion capacitor is currently suggested. The lithium-ion capacitor has a structure of soft aluminum laminated film of electrode laminates therein positive and negative electrodes and separators are layered in an organic electrolyte solution containing lithium-ion. Also, an energy storage module (lithium-ion capacitor module) such as said lithium-ion capacitor used as a single cell or as a plurality of cells connected in parallel or in series to obtain a large amount of electricity is now suggested.
However, constant charging and discharging done with this type of energy storage module causes a single cell to generate heat, thus raising the temperature of the whole module. Especially, when using an energy storage module having a structure encasing a plurality of single cells laminated therein, the heat inside the module will not easily be released, thereby causing the temperature of the module to rise, thus ephemeralizing or damaging the module. Even if there is no such ephemeralization or damage, temperature unevenness within each module causes a difference in capacitance or internal resistance of each cell, thus totally disabling the module.
As described above, to stably operate an energy storage module that often charges and discharges for a long time, it is necessary to sufficiently release the inner heat to the outside of the module. Regarding countermeasures against such a heat problem, some energy storage modules having a heat-releasing structure were conventionally suggested. (See for example Patent References 1, 2 or the like, below). Patent References 1 and 2 describe the energy storage modules forming a heat-releasing pathway in which a good-conductor-of-heat made of a flat metal located between the single cells and the edge is connected to a heat-releasing fin, thus allowing the heat of the single cell to be released out of the container, or the like.    Patent Reference 1: JP-A-2005-57007    Patent Reference 2: JP-A-2009-252501